Here's what our style uses.
No Kyu = White Belt
6th Kyu = Yellow Belt
5th Kyu = Orange Belt
4th Kyu = Blue Belt
3rd Kyu = Green Belt
2nd Kyu = Red Belt
1st Kyu = Brown Belt
Dan = Black Belt
From what I remember, these are the reasons behind the different colors as they relate to old school training methods. Since you only ever got one belt, the belt color kind of changed over time (not to mention getting a little stinky
White Belt = new guy, little to no practice
Yellow Belt = a little practice, some sweat
Orange Belt = more sweat, some dirt
Blue Belt = lots of sweat, dirt, grass
Green Belt = lots of grass, outdoor practice, etc.
Red Belt = Blood!
Brown Belt = Dried Blood!
Black Belt = Lots of practice, dirt, blood, grass, life, etc.